The present invention is directed to integrated circuits. More particularly, the invention provides a system and method for adaptive power supply. Merely by way of example, the invention has been applied to system on a chip. But it would be recognized that the invention has a much broader range of applicability.
Integrated circuits or “ICs” have evolved from a handful of interconnected devices fabricated on a single chip of silicon to millions of devices. Current ICs provide performance and complexity far beyond what was originally imagined. In order to achieve improvements in complexity and circuit density (i.e., the number of devices capable of being packed onto a given chip area), the size of the smallest device feature, also known as the device “geometry”, has become smaller with each generation of ICs. Semiconductor devices are now being fabricated with features less than a quarter of a micron across.
Increasing circuit density has not only improved the complexity and performance of ICs but has also provided lower cost parts to the consumer. An IC fabrication facility can cost hundreds of millions, or even billions, of dollars. Each fabrication facility will have a certain throughput of wafers, and each wafer will have a certain number of ICs on it. Therefore, by making the individual devices of an IC smaller, more devices may be fabricated on each wafer, thus increasing the output of the fabrication facility. Making devices smaller is very challenging, as a given process, device layout, and/or system design often work down to only a certain feature size.
An example of such a limit is power consumption of an integrated circuit system. The power consumption has increased as the performance of the integrated circuit system has improved. But the integrated circuit system is often required to consume a low level of power. For example, the integrated circuit system is portable and thus relies on battery power supply. The portable system may be a laptop computer, a personal data assistant (PDA), a cell phone, a digital camera, a camcorder, or any other device.
These competing demands for high performance and low power consumption have placed significant constraints on system design. Consequently, certain conventional techniques have been used to reduce power consumption. For example, the system turns off some parts that are not in use. In another example, the clock frequency for the system is reduced when the system does not have to perform many tasks. The clock speed often needs to be high enough to support the system for necessary functions. In yet another example, the clock frequency for the system is adjusted based on at least information associated with a workload of the system. In yet another example, the design architecture of the system is modified in order to efficiently utilize the current. In yet another example, the circuit design or device layout is modified to reduce the unused current. In yet another example, the device design is changed to lower the leakage current. But these techniques often increases system complexity with limited effectiveness.
From the above, it is seen that an improved technique for power supply is desired.